My invoice was overdue, I am now paid for it but more quickbooks won't let me mark it as paid. Ive clicked it multiple times to say its paid and then save but nothing

Let's get this sorted out, Fresh

If you intend to mark your invoices as paid in QBO, you must first receive the payment to update their status.

Here's how:

1. Log in to your QBO account.
2. Go to the Sales menu and select Invoices.
   
3. Choose a specific customer and click Receive payment.
4. Fill in the customer details such as Payment Method, Deposit, and the Payment amount that your customer has paid.
   
5. Once done, Save and new.
   

For more detailed information on processing customer payments in QBO, please refer to this article:  Receive and process payments in QuickBooks Online with QuickBooks Payments.

On the other hand, if you are trying to mark your bill invoices as paid and nothing happens, I recommend clearing your browser's cache and cookies to see if that resolves the issue. Clearing the cache can help eliminate excessive data build-up in your QBO.

I’ll share this resource to help you personalize your sales forms in QBO: Customize invoices, estimates, and sales receipts in QuickBooks Online.

Should you need further help with your invoices in QBO, feel free to reach out to us again.